The use of plant
materials to produce industrial products is not a new concept.
With the rise of the petroleum industry, biomass-based
industrial production of fuels and chemicals decreased
substantially in the 1950s and 1960s. The advent of
"biotechnology" in the 1970s, recognition of the limitations of
fossil fuels and emphasis on renewable sources of energy has
rekindled interest in "bioprocessing". Bioprocessing is the
adaptation of biological methods of production to large-scale
industrial use. It thus involves the integration of the
biological, chemical and engineering sciences for the
development of economically viable products and processes.
Competitive advantages in biotechnology may well depend as much
on developments in bioprocess engineering as on innovations in
genetics and molecular biology.

The key step in this technology is the conversion of a
carbohydrate source (e.g., corn starch) to desirable products,
using biological catalysts such as enzymes and microorganisms.
Dextrose (glucose), which is a sugar
that can be produced from corn starch, is the most common
feedstock for these fermentation processes. The corn refining industry is a good
example of the use of renewable resources for producing a
variety of products, from food, feed and fiber to industrial
fuels and chemicals. The most visible example of this
fermentation technology is the use of yeast to produce ethanol,
mostly as an additive to gasoline. US capacity today exceeds 1.5
billion gallons (5.7 million cubic meters) annually. However,
ethanol is only one of several chemicals that can be
manufactured from corn. Others include:

Acetone and
butanol, which are high-value industrial solvents.

Butanediol, an industrial solvent and a precursor to
synthetic rubber.

Lactic
acid, valuable by itself as a commodity chemical, but also
in the future as a raw material for polylactates and acrylates,
which are biodegradable polymers useful in packaging and
medicine.

Acetic
acid, the main component of vinegar, but which has a large
market as an industrial chemical, primarily for the
production of vinyl acetate, monochloroacetic acid, acetic
anhydride, cellulose acetate, acetate solvents, terephthalic
acid, various dyes and pigments and as a solvent in the chemical
process industry. The textile industry uses acetic acid as a
buffering agent in dye baths and for
neutralization. The pharmaceutical industry uses acetic acid to
manufacture vitamins, antibiotics and hormones. The food
industry uses it as an acidulant and for the preservation of
fresh meat products.World production is about 3.5 million tonnes
per year, of which about 2 million tonnes is produced in USA.

It also has potential as an environment-friendly, noncorrosive
highway deicer in the form of calcium-magnesium acetate (CMA), to replace the chloride salts now used
to clear roads in the winter. If even half the salt used on the
nation's highways were replaced with CMA, the demand for corn
would increase by 100-300 million bushels annually and create a
$1-3 billion market for a new corn-based product.

Citric acid, a major acidulant in food products, which is
used in industrial detergents as metal finishing and cleaning
solutions. Much of the citric acid available in the United
States today is produced by corn processors.

The limitations

There are technical constraints in the
use of fermentation to produce these products. A variety of
microorganisms are used in these processes, e.g., yeast
(Saccharomyces cerevisiae) for ethanol; bacteria such as
Lactobacillus delbreuckii for lactic acid; Clostridium
thermoaceticum or Acetobacter aceti for acetic acid
and fungi such as Aspergillus niger for citric acid.
Frequently, the "wild" strain of the microorganism found in
nature is inefficient in that it produces the chemical too
slowly (for example, ethanol fermentation typically takes 24 to
48 hours, acetic acid fermentation 36 to 200 hours) and in too
low a concentration (for example, ethanol is 10 percent of the
fermentation mixture, acetic acid only 2 to 5 percent,
acetone-butanol 1.5 percent). These inefficiencies result in
high fermentation and downstream processing costs, the latter
for removing large quantities of water and for purifying the
chemical. (In contrast, petroleum refiners essentially start
with 100 percent product in the crude oil: they simply have to
distill the oil by heat and blend the fractions to obtain the
desired products).

The solutions

Industrial microbiologists and
biochemical engineers are addressing these inefficiencies in
producing fuels and chemicals from corn. Genetic engineering
can result in microorganisms with improved biosynthetic
capabilities. Researchers at the University of Illinois have
developed strains of Clostridium acetobutylicum that now
produce 40% higher concentration of butanol of parent strains.
Clostridium thermoaceticum has been
mutated and improved to produce 400% higher concentrations of
acetate than the parent wild strain.

Similarly, UI
biochemical engineers have designed continuous bioreactors with productivities
that are 10 to 30 times higher than the technology used today.
In addition, modern separation techniques based on synthetic
membranes are expected to dramatically change the way in which
21st century corn refineries operate.

But .... more limitations

Although these technologies
will improve the manufacturing process, the economics will
depend to a large extent on factors beyond the control of
microbiologists and engineers. The corn itself accounts for
50-70 percent of the cost of ethanol and 20-40 percent of the
cost of organic acids. Energy, much of it produced by coal and
natural gas, probably accounts for another 15-25 percent of the
total corn-refining cost. The prevailing price of oil on the
international market has much to do with the economics of
corn-based versus petroleum-based chemicals. However, petroleum is a finite resource that
is largely imported, whereas corn is annually renewable and
available in abundance within our own borders. One must also
consider the military and political consequences of keeping
imported oil available at low cost.

Considering these
factors, and with continued technological advances, the
cornfields of the Midwest could be as important a source for
fuels and chemicals in the future as the oil fields of the
Middle East are today.